Adipic acid, with the chemical formula C₆H₁₀O₄, is a white crystalline organic compound. As a strong acid, adipic acid is used in many industrial and everyday applications. It is a chemical that is rarely found in nature and has a sour taste. It is typically found exogenously in both urine and blood. Adipic acid was discovered in 1834 in France as a result of the oxidation of a fat.
The chemical and physical properties of adipic acid are as follows:
• Molecular weight: 146.14 g/mol
• Melting point: 152°C
• Boiling point: 337.5°C
• Density: 1.36 g/mL
• Solubility: Moderate in water and alcohol, low in ether
• pKa values: 4.41 and 5.41
Production Methods
• Cyclohexane Method: This is the most common method of adipic acid production. Adipic acid is obtained through the oxidation of cyclohexane with air or nitric acid. Nitrous gas is also released as a byproduct.
• Phenol Method: This is an alternative method for adipic acid production. Phenol is oxidized with oxygen using catalysts, producing water as a byproduct.
• Biochemical Synthesis: This is an innovative production method. Glucose derived from biomass (such as sugar or starch) is fermented by microorganisms, producing carbon dioxide and water as byproducts.
Applications of Adipic Acid:
• Nylon Industry: Adipic acid is one of the most widely used raw materials in the nylon industry. It reacts with hexamethylenediamine to form nylon 6,6 polymer, which is used in fibers, textiles, plastics, filaments, food packaging, and ropes.
• Polyurethane Industry: Adipic acid plays an important role in the polyurethane industry, where it is used in the synthesis of polyester polyols, found in foam, shoe soles, adhesives, and sealants.
• Food Industry: Adipic acid is a widely used food additive, providing sour taste, acidity regulation, buffering, and gelling properties. It is used in jams, canned foods, confectionery, frozen foods, fruit juices, and instant teas.
• Cleaning Industry: Adipic acid is effective in the cleaning sector, where it is used for removing rust from metal surfaces, cleaning lime scale, and eliminating bad odors.
• Corrosion Prevention Industry: Adipic acid is used in corrosion prevention applications. It is found in water treatment systems, boiler water treatment, and aqueous hydraulic fluids, protecting metals from acid vapors, corrosion, and tarnishing.